Centre National De La Recherche Scientifique

France Telecom

Sat (societe Anonyme De Telecommunications)

Odile M Macchi

Christophe Laot

Joel Labat

Sylvie L Marcos

Radelani A Bonnet

Jean-Bernard L Pintaux

Adaptive equalizer for digital communications systems

A terminal is provided for transmitting data over a bidirectional analog channel with echo cncellation coupled to the reception timing, wherein, between an emission circuit and a reception circuit coupled to a bidirectional line by a hybrid coupler, an echo canceller synthesizes an estimated echo from samples of an analog emitted signal, sampled at the same frequency as the received signal, the sampling frequency being controlled by the reception circuit, which is not synchronous with the emission circuit. Such a terminal requires no interpolation filter at the input of the reception circuit and makes possible optimum coupling of the echo canceller with an equalizer.

Terminal for the transmission of data over a bidirectional analog

Echo suppressor with adaptive digital filter for transmission system

An adaptive echo canceller for a full duplex transmission system comprises a cascade arrangement of an adaptive digital filter and an automatic gain control device. The AGC device receives the output signal from the adaptive digital filter and delivers the estimate of the echo signal to the receive line for subtraction. It has a multiplier receiving the output signal and a signal representative of the multiplication factor from a gain adaptation circuit. A separate gain change circuit is connected to receive the output signal from the adaptive digital filter and simultaneously modifies the tap coefficients of said filter and the multiplication factor of the AGC device in opposite directions for maintaining the output of the adaptive digital filter in a predetermined range.

Adaptive echo canceller with AGC for transmission systems

Growing community of inventors

Orsay, France

Odile M Macchi